Without modifying the source code, how can i trace which functions are called and with what parameters, when some function(say func100 in the following example) is in
You can look into log4cxx, a project hosted by the apache foundation. I know that log4j, the java variant allowed you to set the sensitivity, and you could track every single thing that was done in the program. Maybe that the c++ variant is the same, but there are several alternatives-there's an aspect oriented c++ compiler, and you can define an aspect across all functions, and have it catch and print the variables. Another alternative is to use a debugger.
To summarize: debugger, log4cxx or AOP